[Thunderguts]

I found this in the training manual:

Intelligent Alternator Control (IGR) No fuel is drawn from the tank in overrunning mode. The injectors in the fuel injection system are shut off. The engine is driven by the kinetic energy from the wheels. The alternator generates the maximum possible electrical output and supplies the electrical equipment. The DME is in communication with the alternator and the intelligent battery sensor, which detects the charge level of the battery, and charges the battery with the maximum possible voltage.

I don't know how long it takes for the ECU to determine it's in "overrun mode," but the instant it does, all fuel is cut off. That explains why it's so slow to react when you try to get back on the throttle. This also explains why it's really quiet in overrun mode with no pops and cracks from the exhaust. I really wonder if there is a way to code this out to improve throttle response.